I told you all I would have questions in my introduction post

I didn't waste any time. So as my title states, I have poopie questions. We just got Dexter a week ago and he is 8 weeks old. For a tiny little thing, he's been doing pretty good with the potty training. However, we have a crate that is the appropriate size for him (they can't get any smaller, lol) and he pee's and poops in there. I bought the special spray to clean such messes (and follow the instructions doing so). I had also made a divider (since I don't know where to get one) out of thick cardboard paper, to prevent him from making such messes. That didn't help & I threw the divider out. This tends to happen more so at night, even after I get up at 1am, or 3am to take him out. We also bought him a pet playpen. We put him in said playpen when we are going to go out, well when we get back we can see that he pooped, but no poopies anywhere to be found. He eats his poop sometimes. So I went to PetSmart and tried to look for the pills that you put in his food to prevent him from doing that. Except, it's for dogs 20lbs & over. So I read that putting seasoning salt could help prevent that. Except, I'm worried about him eating salt. Do you all have any recommendations? Any help with my problems would help.
Oh also, my hubby bought him GNC Ultra Mega High Calorie Booster, again it states dogs 20lbs & over. But what I did was just barely swipe some on my finger and have him lick it. He didn't bother, so I put it in his mouth. Well, not even a minute later he vomited. I know it was the Cal. Booster, he's never done it again, because I haven't given him any more.
I'd appreciate any and all help I get. Thank you